title: Influences of knee flexion angle and portal position on the location of femoral tunnel outlet in anterior cruciate ligament reconstruction with anteromedial portal technique.
abstract: OBJECTIVE
  To evaluate the influences of knee flexion angle and portal position on the location of femoral tunnel outlet in anterior cruciate ligament (ACL) reconstruction with the anteromedial (AM) portal technique.
  
  
  METHODS
  We recruited 6 volunteers with 12 normal knees. Each knee was flexed 120° or 135° and scanned with an open MRI. A 3D knee model was created. Virtual femoral tunnels were created on the footprint of the AM bundle and the posterolateral (PL) bundle of the ACL from three arthroscopic portals: the standard AM portal, the far medial and low portal, and the far medial and high (FMH) portal. The location of the femoral tunnel outlet was evaluated by comparing to the dissected cadaveric knee.
  
  
  RESULTS
  Both increased flexion angle and lowering the drilling portal have a similar influence on the femoral tunnel outlet by moving them anterior and distally. Medialization of the portal moves them posteriorly and distally. PL tunnels created on the 120° knee model are more likely to be located under the lateral head of the gastrocnemius especially when they are drilled through the AM or FMH portals.
  
  
  CONCLUSIONS
  If the femoral tunnel outlet is located under the soft tissue such as gastrocnemius attachment, suspension fixation devices may lapse into fixation failure by sitting on the soft tissue rather than the cortex bone surface. It is more desirable to drill in 135° knee flexion rather than 120°, and through a lower portal, to avoid creating the femoral tunnel outlet under soft tissues.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
authors.forename: Kanji
authors.initials: K
authors.lastname: Osaki
authors.forename: Ken
authors.initials: K
authors.lastname: Okazaki
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Tashiro
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Matsubara
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Iwamoto
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001182:Arthroscopy; D005260:Female; D005269:Femur / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D011187:Posture; D016059:Range of Motion, Articular